Why not install an AOSP ROM and pretend the customizations aren't there? Most of the AOSP ROMs are pretty close to "stock" out of the box.

When I had my nexus it had a custom ROM on it within an hour.

Sent from my LG-VS980 using Tapatalk

Most of the custom ROMs, when in their early days, have stock Android, are pretty stable, but as the features are added, they start misbehaving.
Not talking about SODs or Random reboots in G2 in the early days.
Issues with the framework, etc.

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